High-efficiency refining process for molten metal silicon under synergistic effect of various fields

Abstract

The invention relates to the technical field of high-efficiency refining of molten metal silicon, and discloses a high-efficiency refining process of molten metal silicon under the synergistic effect of multiple fields, which comprises the following steps: S1, placing molten metal silicon in a refining device which can apply a controllable temperature gradient field and an external electric field; s2, by regulating and controlling the size and the direction of the temperature gradient field, metal impurities are directionally migrated to a low-temperature area in the melt under the action of thermal diffusion and are enriched; s3, an external electric field is applied at the same time, and non-metal impurities are directionally migrated to an electrode area and enriched under the electromigration effect by regulating and controlling the type, intensity and frequency of the electric field; s4, performing cooperative control on the temperature gradient field and an external electric field; and S5, carrying out physical isolation or online removal on the enriched impurity region. Compared with the prior art, the device and the method have the advantages that metal and nonmetal impurities are respectively driven to directionally migrate and enrich, so that efficient separation of the impurities and deep purification of the silicon melt are realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-efficiency refining of molten metallic silicon, in particular to a high-efficiency refining process of molten metallic silicon under the synergistic action of multiple fields. BACKGROUND

[0002] Industrial silicon, as a key basic material in the fields of information industry, new energy and advanced materials, directly affects the performance of the final product. At present, industrial silicon refining mainly adopts traditional methods such as oxygen refining, flux refining, gas blowing and directional solidification. Most of these methods rely on the physical diffusion, chemical reaction or solid-liquid phase separation effect of impurities, and there are a series of common bottlenecks.

[0003] In the prior art, for boron, phosphorus and other impurities with similar physical and chemical properties to silicon, it is difficult to achieve efficient removal by conventional methods. The low migration rate of impurities leads to long refining period and high energy consumption, and some processes may also introduce secondary pollution or generate a large amount of waste slag. In addition, the traditional process lacks directional control ability for the migration path and enrichment behavior of impurities, affecting the consistency of product purity and process stability.

[0004] Therefore, it is necessary to develop a new refining process that can realize directional migration, efficient enrichment and separation of impurities, thereby improving the efficiency of impurity removal while reducing energy consumption and environmental load. SUMMARY

[0005] (I) Technical problems to be solved

[0006] The technical problem to be solved by the present application is to drive the directional migration and enrichment of metal and non-metal impurities respectively by the coupling effect of temperature gradient field and external electric field, so as to realize the efficient separation of impurities and the deep purification of silicon melt.

[0007] (II) Technical solutions

[0008] To solve the above technical problems, the technical solution provided by the present application is a high-efficiency refining process of molten metallic silicon under the synergistic action of multiple fields, comprising the following steps:

[0009] S1, placing molten metallic silicon in a refining device, the device being capable of applying controllable temperature gradient field and external electric field;

[0010] S2, by adjusting the size and direction of the temperature gradient field, the metal impurities are driven to migrate to the low-temperature region in the melt and enrich under the action of thermal diffusion;

[0011] S3, at the same time, an external electric field is applied, and by adjusting the type, intensity and frequency of the electric field, the non-metallic impurities are driven to migrate to the electrode region and enrich under the action of electric migration;

[0012] S4, the temperature gradient field and the applied electric field are cooperatively controlled to realize the synchronous, directional and efficient separation and enrichment of metal impurities and non-metal impurities;

[0013] S5, the enriched impurity region is physically isolated or removed online to complete the deep purification of the metal silicon.

[0014] As an improvement, in step S2, the temperature gradient field is an axial temperature gradient, and the gradient range is 10-200 K / cm, preferably 50-150 K / cm.

[0015] As an improvement, in step S3, the applied electric field is a direct current electric field or an alternating current electric field, and the electric field strength is 0.1-10 V / cm, and the frequency is 0-1000 Hz.

[0016] As an improvement, in step S3, the electrode uses inert electrode material resistant to high temperature and silicon melt corrosion, including one or composite material of graphite, molybdenum, tungsten or silicon carbide.

[0017] As an improvement, in steps S2 and S3, the metal impurities include one or more of iron, aluminum, calcium and titanium, and the non-metal impurities include boron and phosphorus.

[0018] As an improvement, the removal rates of boron and phosphorus are not less than 60% and 70% respectively, and the comprehensive removal rate of metal impurities is not less than 70%.

[0019] As an improvement, in step S4, based on the impurity migration model established by first-principle calculation and molecular dynamics simulation, the cooperative configuration of temperature gradient and electric field parameters is optimized.

[0020] As an improvement, the process further comprises a step of: during the refining process, using a high-temperature melt in-situ monitoring system to monitor the impurity migration behavior in real time, and based on data mining and pattern recognition, the steps S2 to S4 are intelligently feedback controlled.

[0021] As an improvement, in step S4, the gradient value of the temperature gradient field, the strength and frequency of the electric field, and other key process parameters are cooperatively optimized by orthogonal test design and response surface analysis method.

[0022] As an improvement, in step S3, the electrode structure is symmetric or asymmetric layout to induce the formation of flow field inside the melt which is beneficial to the directional migration of impurities.

[0023] (Three) beneficial effects

[0024] Compared with the prior art, the advantages of the present application are that: through the synergistic effect of the temperature gradient field and the electric field, the directional migration of metal and non-metal impurities is realized, the pertinence and efficiency of impurity separation are improved, the use of slagging agent in traditional chemical refining is avoided through the synergistic control of physical fields, and the secondary pollution and waste slag production are reduced; the precise optimization and process controllability of process parameters are realized through the combination of theoretical simulation and intelligent monitoring, and the process stability and repeatability are improved. The process is suitable for pilot and industrialization scale, and provides a feasible technical path for green and efficient preparation of high-purity industrial silicon. DETAILED DESCRIPTION

[0025] The invention content of the present application will be further described in detail below in combination with specific embodiments, but it should not be understood that the scope of the subject matter of the present application is limited to the following examples.

[0026] Example 1

[0027] A high-efficiency refining process for molten metallic silicon under the synergistic action of multiple fields, comprising the following steps:

[0028] S1, placing the molten metallic silicon in a refining device, the device being capable of applying a controllable temperature gradient field and an external electric field;

[0029] S2, by adjusting the size and direction of the temperature gradient field, the metal impurities are directionally migrated to the low-temperature region in the melt under the action of thermal diffusion and enriched, the temperature gradient field is an axial temperature gradient, and the gradient range is 200K / cm, preferably 150K / cm;

[0030] S3, an external electric field is applied at the same time, by adjusting the type, intensity and frequency of the electric field, the non-metallic impurities are directionally migrated to the electrode region under the action of electromigration and enriched, the external electric field is a direct current electric field or an alternating current electric field, the electric field strength is 10V / cm, the frequency is 1000Hz, the electrode uses inert electrode material resistant to high temperature and corrosion of silicon melt, including graphite, the metal impurities include iron, aluminum and calcium, the non-metallic impurities include boron and phosphorus, the removal rates of boron and phosphorus are not less than 60% and 70% respectively, and the comprehensive removal rate of metal impurities is not less than 70%, the electrode structure is symmetric or asymmetric layout to induce the formation of flow field inside the melt which is beneficial to the directional migration of impurities;

[0031] S4, the temperature gradient field and the external electric field are synergistically controlled to realize the synchronous, directional and efficient separation and enrichment of metal impurities and non-metallic impurities, based on the impurity migration model established through first-principle calculation and molecular dynamics simulation, the synergistic configuration of temperature gradient and electric field parameters is optimized, and the gradient value of the temperature gradient field, the intensity and frequency of the electric field are synergistically optimized by orthogonal test design and response surface analysis method;

[0032] S5. Physically isolate or remove the enriched impurity areas online to complete the deep purification of metallic silicon. During the refining process, use a high-temperature melt in-situ monitoring system to monitor the impurity migration behavior in real time, and use data mining and pattern recognition to perform intelligent feedback control on steps S2 to S4.

[0033] Example 2

[0034] A highly efficient refining process for molten metallic silicon under the synergistic effect of multiple fields includes the following steps:

[0035] S1. Molten metallic silicon is placed in a refining apparatus, which is capable of applying a controllable temperature gradient field and an external electric field.

[0036] S2. By adjusting the magnitude and direction of the temperature gradient field, the metal impurities are directionally migrated to the low-temperature region of the melt and enriched under the action of thermal diffusion. The temperature gradient field is an axial temperature gradient with a gradient range of 10K / cm, preferably 50K / cm.

[0037] S3. Simultaneously, an external electric field is applied. By adjusting the type, intensity, and frequency of the electric field, non-metallic impurities are directed to migrate to the electrode region and accumulate under electromigration. The external electric field is a DC or AC electric field with an electric field strength of 0.1 V / cm and a frequency of 1 Hz. The electrode is made of inert electrode material that is resistant to high temperature and silicon melt corrosion, including graphite, molybdenum, and tungsten. The metallic impurities include iron, aluminum, calcium, and titanium. The non-metallic impurities include boron and phosphorus. The process removes boron and phosphorus at a rate of not less than 60% and 70%, respectively, and the overall removal rate of metallic impurities is not less than 70%. The electrode structure is symmetrical or asymmetrical to induce the formation of a flow field inside the melt that is conducive to the directional migration of impurities.

[0038] S4. The temperature gradient field and the applied electric field are controlled in a coordinated manner to achieve synchronous, directional, and efficient separation and enrichment of metallic and non-metallic impurities. Based on the impurity migration model established by first-principles calculations and molecular dynamics simulations, the coordinated configuration of temperature gradient and electric field parameters is optimized. Orthogonal experimental design and response surface methodology are used to coordinately optimize the key process parameters of temperature gradient field gradient value, electric field intensity, and frequency.

[0039] S5. Physically isolate or remove the enriched impurity areas online to complete the deep purification of metallic silicon. During the refining process, use a high-temperature melt in-situ monitoring system to monitor the impurity migration behavior in real time, and use data mining and pattern recognition to perform intelligent feedback control on steps S2 to S4.

[0040] Example 3

[0041] The molten industrial silicon is injected into a refining device with double field application function. The device forms an axial temperature gradient with a gradient value of 80 K / cm, so that metal impurities such as iron and aluminum migrate to the low-temperature area and are enriched. A direct current field with a strength of 5 V / cm is applied synchronously to drive non-metallic impurities such as boron and phosphorus to migrate to the anode area.

[0042] The synergistic parameters of the two fields are optimized through the first principle and molecular dynamics model established in the early stage. The high-temperature nitrogen gallium in-situ monitoring system is used to track the change of impurity concentration in real time, and the data system is used for process feedback control.

[0043] After the refining is completed, the silicon material in the head and electrode area which is enriched with impurities is removed by physical means. The boron removal rate reaches 65%, the phosphorus removal rate is 75%, and the comprehensive removal rate of metal impurities is more than 75%.

[0044] In another experimental example, the temperature gradient is increased to 120 K / cm, an alternating current field is used, the frequency is set to 50 Hz, and the electric field strength is 2 V / cm. Graphite and silicon carbide composite materials are used for the electrode, and the electrode is arranged in an asymmetric manner to strengthen the convection inside the melt.

[0045] The optimal combination of gradient, field strength and frequency is determined by combining orthogonal test and response surface analysis. After refining, the boron and phosphorus removal rates are 68% and 78% respectively, the metal impurity removal rate is close to 80%, and the overall energy consumption of the process is reduced by about 20% compared with the traditional method.

[0046] Although the embodiments of the present application have been shown and described, it can be understood by those skilled in the art that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the present application, the scope of the present application is defined by the appended claims and their equivalents, in general, if a person skilled in the art is inspired by it, without departing from the purpose of the present application, without creative design, similar structure and embodiments of the technical scheme should belong to the protection scope of the present application.

Claims

1. A high-efficiency refining process for molten silicon under the synergistic action of multiple fields, characterized in that, The process comprises the following steps: S1, placing molten silicon in a refining device capable of applying a controllable temperature gradient field and an applied electric field; S2, by regulating the size and direction of the temperature gradient field, the metal impurities are directionally migrated to the low temperature region in the melt under the action of thermal diffusion and enriched; S3, while applying an external electric field, by regulating the type, intensity and frequency of the electric field, the non-metallic impurities are directionally migrated to the electrode region under the action of electromigration and enriched; S4, the temperature gradient field and the applied electric field are synergistically controlled to realize the synchronous, directional and efficient separation and enrichment of metal impurities and non-metallic impurities; S5, the enriched impurity region is physically isolated or removed online to complete the deep purification of the metal silicon.

2. The process according to claim 1, characterized in that, In step S2, the temperature gradient field is an axial temperature gradient, and the gradient range is 10-200 K / cm, preferably 50-150 K / cm.

3. The process according to claim 1, characterized in that, In step S3, the applied electric field is a direct current electric field or an alternating current electric field, and the electric field strength is 0.1-10 V / cm, and the frequency is 0-1000 Hz.

4. The process according to claim 1, characterized in that, In step S3, the electrode uses inert electrode material resistant to high temperature and corrosion of silicon melt, including one or composite material of graphite, molybdenum, tungsten or silicon carbide.

5. The process according to claim 1, wherein the process is characterized by, In steps S2 and S3, the metal impurities include one or more of iron, aluminum, calcium and titanium, and the non-metallic impurities include boron and phosphorus.

6. The process according to claim 1, wherein the process is characterized by, The removal rate of the process for boron and phosphorus is not less than 60% and 70% respectively, and the comprehensive removal rate of metal impurities is not less than 70%.

7. The process according to claim 1, wherein the process is characterized by, In step S4, based on the impurity migration model established by first-principle calculation and molecular dynamics simulation, the synergistic configuration of temperature gradient and electric field parameters is optimized.

8. The process according to claim 1, wherein the process is characterized by, The process also comprises a step of: during the refining process, using a high-temperature melt in-situ monitoring system to monitor the impurity migration behavior in real time, and based on data mining and pattern recognition, the steps S2 to S4 are intelligently feedback controlled.

9. The process according to claim 1, wherein the process is characterized by, In step S4, the gradient value of the temperature gradient field, the intensity and frequency of the electric field are synergistically optimized by orthogonal test design and response surface analysis method.

10. The process as claimed in claim 1, wherein the process is characterized by, In step S3, the electrode structure is symmetric or asymmetric layout to induce the formation of flow field inside the melt which is beneficial to the directional migration of impurities.